System for comparing synchronized wave signals



May 31, 1949. s LOBEL 2,471,530

SYSTEM FOR COMPARING SYNCHRONIZED WAVE SIGNALS Filed Sept. 12, 1945 SEYMOUR LO BEL BY $42M y w/ ATTORNEYS Patented May 31, 1949 PAT EN T F Fz'l CE SYSTEMF-O-R COMPARING SYNCHRONIZED WAVE SIGNALS New York Application September 12, 1945, Serial No.'615,895

-1 Claim. 1

"This invention relates to systems for comparing synchronized wave signals and, while it is of general-application, it is particularly suitable for comparing the input and output signals of a wave-signal translating apparatus-in order to determine distortion, time delayor other translating characteristics of the apparatus.

' In the translation ofwave signals through any given apparatus, it is frequently desirable to'be able to compare directly and continuously the inputand output waves in order to determine the translating characteristics of the apparatus, such as amplitude or frequency distortion, time delay, etc. This comparison is particularly important in-the case of pulse signals, such as used to a large extent in various types of radio beacons, direction finders and-range finders. This is due to the fact that the steepness of'the leading and trailing edges of such pulses and the sharpness of their corners-are particularly susceptible to distortion or degeneration in wave-signal translating apparatus' and to the fact that the precise timing of their leading'and trailing edges is of controlling importance in the systems in which they are utilized. Therefore, any time delay introduced bysuch apparatus must be, precisely d'eterminedand taken into account in the de'sig-nand operation-of the system of which the apparatus is a-part.

1 It =is-an object of the invention, therefore, to provide a new and improved system forcomparing synchronized wave signals which is particularly*useful'ior comparing the input and output signals or a wave-signtl translating apparatus.

lt 'is another bbjectof the'invention to, provide-anew and impr'oved system for comparing synchronized wave signals of" the type described which" provides a"'di-rect and continuous comparison of two *related'waves bymeans of which any' distortion "or time de'lay, or both, may be readily observed.

'IfiaccoFda-nceWi-th the invention, a system for comparing two related" synchronized wave signals oomp'rises vacuum-tube repeater means having input circuit 'meansand output circuit means arid means -for individually applying the signals to' theinput circuit means. The system also includes anoscillogra'phic deviceymeans'for' scanningthe' devicesynchronously with the signals, means for-deflecting'thebeamof the device, and circuit means for coupling the deflecting means tozthe output cirouit means. The system further includeshmeans ioirperlodically rendering the repeater means tefiectivet to translate the two signals -..alternately =:and.::means l for :"modirying the:

excitation of the'deflecting means laterally to displace the beam -during alternate periods, whereby laterally displaced traces of the signals are developed simultaneously by the oscillographic device.

For a better understanding of the invention, together with other-and further objects thereof, reference is had to the following description taken in connection -=with the accompanying drawings while its scope will be pointed out in the appended claim.

Referring now to the drawing, the single figure is a circuit diagram, partly schematic, of a complete system for comparing the input and. output signals of a wave-signal translating apparatus, such as a wave filter.

Referring now to' the" drawing, there is represented a system for comparing two related. synchronized waves, forexample the signal input. and the signal-output of a wave-signal translating apparatus, such' as a band-pass wave filter H) comprising series inductance arms 10a and lllb and a shunt capacitance-arm 10c and having in-v put terminals 40d and output terminals Ille. Signals are applied to the input terminals ltd of the apparatus 10 from any-suitable source, such as a signal generator I I, while theoutput signals of the apparatus lO'a-re derived from terminals We and applied to the system output terminals l2 for utilization in any desired manner.

The system also includes vacuum-tube repeater means having input circuit means. and output circuit means andmeans for individually applying the inputand-output signals of the apparatus H) to the input circuit means. Specifically, the, vacuum-tube repeater means comprises two vacuum-tube repeater paths whichmay be in the form of separate vaccum-tube repeaters or, as shown, a duplex vacuum-tube repeater [3 'in which one repeater path comprises an anode 13a, a control electrode -l3banda cathode I and the other repeater pathcomprises. an anode 13d, control electrode13e--and a cathode IS The two repeater pathsof the tube I3 have individual.

1 input circuits, that is their control electrodes I31) 1 and l3e are connected to the input andoutput terminals IOd-and- Me, respectively, of the'wavesignal translatingapparatus- 40 through coupling condensers M and 15, respectively. The two re- 1 p'eater paths have a'comm'on output or load circuit in the form of-a common cathode loadre sistance means comprising resistors 16 and I! in parallel and provided with adjustable contacts IGa-and- Ila, respectively. The input circuits or electrodes of the"tWOiIBDBZIhBFPEthS of tube 13;

3 s of different values individi ial ting e thereto which may be derived by connec control electrodes I31) and I3e to electr callly spaced points on the resistance network lo, I for example to the adjustable contacts I6a and Ila, respectively.

The system of the in have biasing mean vention also includes an oscillographic device such as an oscilloscope I: having a fluorescent screen I8a, a basbel ancathode-ray forming assembly IBb. Smta e op erating potentials for the cathode-ray fDlmllig assembly I8 may be derived from a powersu lipdy unit I9. There are also provided means me u g ing a scanning generator synchronized by (zine of the signals to be compared for scanning I oscilloscope I8 synchronously with the signai This means may be in the form of a saw-tog};J

wave generator 29 having input terminals a connected to be synchronized by the signal genas illustrated, and having output ternnected to a pair of time-base deoscilloscope I8. There erator II. minals 29b co flecting plates I30 of the are also provided means for deflecting the beam oscilloscope I8 and means for coupl1ng l ie dfflecting means to the output circuit means, that is to the common load resistance networ I6, ll of the repeater means. Specifically, the oscilloscope I8 is provided with a pa1r of signaldeflecting plates I8d which are coupled across the resistance network I6, I! through a coupling 2|. l ii s ystem of the invention also includes means for periodically rendering the repeater means effective to translate the two signalsto be compared alternately at a periodicitywhich is preferably small compared to the persistence of vision of the screen I8a of the oscillographic device and at a frequency which is preferably high compared to the fundamental frequency of the signals. To this end, there is provlded an electromagnetic relay 22 and a rectifier tube 23 connected in series and adapted to be excited from commercial alternating-current supply 011'- cuit terminals 24 through a transformer 25. The relay 22 is provided with a pair of stationary contacts 22a. 22b and a movable contact 220 with vibrates between the contacts 22a, 22b for connecting the load circuit resistance means I6, I! alternately in circuit with the two repeater paths of the vacuum tube I3. specifically between the cathodes I30 and I3 and ground, periodically to vary the repeating ratio of the repeating means I3. In order to prevent complete interruption of the repeater paths of the vacuum tube I3 there are provided auxiliary cathode resistors 26 and 21 permanently connected between the cathodes I30 and I3), respectively, and ground.

In explaining the operation of the comparing system of the invention. it will be assumed that the input signal from the signal generator II is in the form of a pulse wave, such as represented by curve A adjacent the generator II. This signal is applied to the wave filter In and, due to the translating properties of this filter. is somewhat distorted or degenerated and simultaneously delayed so that the signal appearing at its output terminals Ice does not exactly correspond in Wave form timing with the input wave. Assuming at the initial instant that the rela 22 is effective to close its contacts 220:, 220. the inout nal to the filter II] is applied to the control electrode 53b of tube I 3 and the repeater path I3a, I31), I 30 of this tube acts in a conventional manner to develop across its cathode load circuit, comprising the resistors I6 and I! in parallel, a faithful reproduction of the input signal of curve A. This signal is applied through the coupling condenser 2| to the deflecting plates I803 of the oscilloscope I8. Simultaneously, a synchronous saw-tooth wave developed by the generator 20 is applied to the time base deflecting plates I and the resultant of these two deflections normal to each other is reproduced on the screen I8a as curve A1, which is a faithful reproduction of the input signal of curve A. The vertical position of curve A1 on the screen I8a is determined by the bias potential applied to the control electrode I31) which, in turn, is controlled by adjustment of contact Ilia of cathode-load resistor I6. By suitably adjusting this contact, curve A1 may be made to appear in any desired vertical position on the screen l8a.

An instant of time later, the relay 22 closes its contacts 22b and 220 thereby including the cathode load resistance I6 and I! in repeater path 53d, I3e and I3) of tube I3 so that this repeater path is effective to reproduce across the cathode load resistance the output signal derived from terminals We and impressed on the control electrode 3e through coupling condenser I5. The oscilloscope i8 is then effective to reproduce on the screen I8 curve A2 which is a faithful reproduction of the signal output of the wave filter ill. The vertical position of curve A2 is determined by adjustment of contact l'la of resistor I 1. Thus the contacts Ifia and I'Ia may be adjusted to cause curves A1 and A2 to appear vertically displaced at an appropriate distance which may be related to the amplitudes of the signals represented thereby so as to avoid interference of curves A1 and A2. It will be noted that the curve A2 is delayed with respect to the curve A1 by an interval t1 and that the wave form of the curve A2 is distorted or degenerated somewhat with respect to the input curve A1. A comparison of the curves A1 and A2 thus gives a direct indication of the translating properties of the wave filter Ill.

In case the terminals 24 are excited with a 60- cycle alternating current, the transformer 25 and rectifier 23 are effective to apply to the relay 22 a BO-cycle pulse wave comprising half-cycles of the supply wave of a given polarity. The relay 22 so excited is eifective to vibrate its contact 220 at a frequency of 60 cycles and thus periodically rendering the repeater paths I3a, I31), I30 and ltd, I30, I31 alternately effective to translate the input signal at the terminals Id and the output signal at the terminals Ifle. Thus the curves A1 and A2 are alternately traced at a periodicity which is small compared to the persistence of vision of the fluorescent screen I8a so that the curves A1 and A2 appear to persist and may be continuously and directly compared. The system is suitable for comparing signals of a frequency either higher or lower than the frequency of operation of the relay 22. If higher, complete pulse trains will be traced during each interval .of operation of one of the repeater paths of the tube I3. If lower, portions of the curves A1 and A2 will be traced alternately. Thus, the system of the invention provides means for directly and continuously comparing two related synchronized signals such as the input and output signals of the wave-translating apparatus.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

I claim:

A system for enabling visual comparison of two related synchronized wave signals comprising, two vacuum-tube repeater paths having individual input circuits and a common cathode load resistance means, said input circuits being returned to electrically spaced points on said resistance means, means for individually applying said signals to said input circuits, an oscillographic device, means for scanning said device synchronously with said signals, means for defleeting the beam of said device, circuit means for coupling said deflecting means to said resistance means, and means for periodically connecting said resistance means alternately in circuit with said repeater paths, whereby laterally displaced traces of said signals are developed simultaneously by said device.

SEYMOUR LOBEL.

6 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Electronic Industries, September 1944, pp. 84, 85 and 224. 

